Evaluating the quality of students' programs is necessary for better teaching and learning. Although many innovative learning environments for computer science have been introduced, the scarcity of program evaluation frames and tools is a demanding issue in the teaching practice. This study examined the quality of students' Scratch programs by utilizing Dr. Scratch and by analyzing codes based on four computational concepts: conditions, loops, abstractions, and variables. Twenty-three Scratch programs from two classes of pre-service teachers from a university were examined. Dr. Scratch results revealed that Scratch programs demonstrated a middle level of competency in computational thinking. The analysis of computational concepts suggested that students had a sufficient understanding of the main concepts and demonstrated computing competency by applying the concepts into their programs. The study also discussed inefficient programming habits, instructional issues utilizing Scratch, and the importance of problem decomposition skills.